Sheet break detector



Dec. 1, 1964 I... HORNBOSTEL, JR 3,

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L BY v fwrmsys United States Patent 3,159,028 SHEET BREAK DETECTOR LloydHornbostel, Jr., Beloit, Wis., assignor to Beloit Corporation, acorporation of Wisconsin Filed Feb. 15, 1961, Ser. No. 89,452 8 Claims.(Cl. 73-159) The present invention relates to improvements in mechanismfor detecting breaks in a sheet such as a travelling paper web in apaper machine.

Sheet or web break detectors have been employed for detecting a break ina travelling sheet of material and used in winding and unwindingmachines in the paper industry, in printing presses, and in other fieldsand for other materials. The embodiment of the present invention findsuses in these various fields but is well suited to use for detecting abreak in a travelling paper web and will be described for this use.

Break detectors have been employed which require engagement with themoving sheet and these have not been wholly satisfactory in that theyfail from interference with foreign materials and engagement with a fastrunning sheet is disadvantageous such as with circumstances where damageto the sheet can occur. Light beam type detectors have also beenemployed and these have disadvantages in that they will fail frominterruption of the beam by foreign materials, will detect breaks onlywhen an actual tear reaches the unit, and cannot be used in allenvironments.

An object of the invention is to provide an improved sheet breakdetector utilizing a stream of air flowing against the travelling sheetwherein movement of the sheet out of its normal running plane canbesimple and immediately detected so that loss in tension in the sheetresulting from the break will enable detection before the actual tearreaches the detecting unit.

Another object of the invention is the provision of an improved sheetbreak detector which eliminates the need for contact with the travellingsheet and cannot damage or mar sheets which are coated or have afinished surface.

A further object of the invention is to provide an improved mechanismfor detecting breaks in a moving web which can be simply and quicklyremoved from the operating position for rethreading of the machine.

A feature of the invention is the provision of a sheet break detectoremploying a first means for directing a stream of air against thesurface of a moving web travelling in a predetermined running plane withsecond means for detecting the effect on the first means of movement ofthe web out of the running plane so that breaks in the web and otherconditions which cause the sheet to move out of its running plane areimmediately detected.

Other objects, advantages and features will become more apparent withthe teaching of the principles of the invention in connection with thedisclosure of the preferred embodiments thereof in the specification,claims and drawings, in which:

FIGURE 1 is a side elevational view shown in somewhat schematic form ofa sheet break detector embodying the principles of the presentinvention;

FIGURE 2 is a side elevational view shown partially in section andillustrated somewhat schematically of another form of sheet detectorembodying the principles of the present invention;

FIGURE 3 is a vertical sectional view taken substantially along lineIII-III of FIGURE 2;

FIGURE 4 is a side elevational view similar to FIG- URE 2 showing theparts of the mechanism in position for threading a fresh web into place;and

FIGURES 5 and 6 are vertical sectional views taken through a modifiedform of the mechanism shown in FIGURES 2 through 4.

3,159,028 Patented Dec. 1, 1964 As shown on the drawings:

As shown in FIGURE 1 the travelling sheet or web W moves in thedirection indicated by the arrowed line. During normal operation the webis positioned in a normal running plane, but if the web should tear itwill lose its tension and be free to shift laterally of the runningplane. In accordance with the invention, a jet of air is directedlaterally against the web and the normal running tension resists theforce of the air. However, when the sheet breaks, the sheet loses itstension and the effect on the air stream of the reduction in resistanceis detected. A tubular conduit 10 is provided with an orifice or nozzle11 positioned adjacent the surface of the web W in its running plane.The nozzle is positioned so that the direction of the air stream asindicated by the broken line A forms an acute angle 0 with the web W andis directed toward the oncoming web.

The conduit 10 is supplied with a continual flow of air undersubstantially constant pressure through a supply line 12 from an airsupply S. If used in a paper machine the air supply may be taken fromthe pressurized supply S that is normally available in paper makingmachines. a

The supply line 12 connects to the conduit 10 through a pressureregulating valve 13. A pressure gauge 14 may be conveniently connectedin a line downstream of the pressure regulating valve 13 to indicate thepressure in the conduit 10.

Also connected to the conduit 10 downstream of the pressure regulatingvalve 13 is a pressure switch 15 which is responsive to the pressure inthe conduit 10 and may be connected to operate mechanism in response toa change in pressure in the conduit 10. As shown, the pressure switch 15is connected to a signal 16 supplied with electricity through a line 17.

In operation, the presence of the web W, prevents the free escape of airfrom the conduit 10, and the pressure in the conduit 10 will bedependent upon the size of the gap G between the opening of the nozzle11 and the web W. With breakage of the web the tension is lost and theweb is immediately free to move away from the nozzle 11 resulting in adrop in pressure in the conduit 10 and in actuation of the pressureswitch 15. The pressure switch may be attached to a warning device asshown or to cut off traverse mechanism or other control mechanism whichoperates in response to breakage of the web or a loss of tensionthereof.

Thus the nozzle 11 with the conduit 10 and air supply provide a firstmeans for directing a stream of air against the surface of the web W inits normal running plane and the pressure responsive mechanism 15provides a second means for detecting the effect on the first means ofmovement of the web out of the running plane.

As an example of operation a preferred structure has been found in anarrangement wherein the gap between the nozzle 11 and the running planeof the web W is within the range of A; to /2 inch usinga /2 inch conduit10 and providing a 1 inch diameter flare to the edge 11a of the nozzle11. 60 to and the air supply S of 60-90 pounds per square inch isreduced to 3 pounds per square inch by the valve 13. The pressure switch15 is adjustable between 1.0 and 1.8 pounds per square inch.

The arrangement of FIGURES 2 through 4 shows a hollow tube 20 cut off atan angle at its end to provide an orifice or nozzle 21 for directing astream of air against a travelling paper web W. The reaction force ofthe air supports the nozzle 21 above the web with a gap G. With breakageof the web W and a resultant loss of tension the web is free to movedownwardly and the nozzle 21 of the tube 20, which is pivotally mounted,will move downwardly to actuate a switch 22 mounted The angle 0 is inthe range of' on the tube. The switch 22 may take various forms and asillustrated a mercury switch is provided which will be connected to asignal device 22a or other mechanism to be actuated in response tobreakage of the web W.

As shown in FIGURE 3, the tube 20 is supported on a hollow supply shaft24 which communicates with the hollow inside of the tube 20 and ispivoted in a vertical support bracket 23. The support bracket isprovided with a fitting 25 for connection of an air supply hose 26 sothat the inside of the tube 20 is provided with a continuous flow ofpressurized air.

Air is supplied from an air pressure source S to which is connected aline or a tube 26 and the supply is furnished at a constant pressurethrough a pressure reduction valve 27. The flow of air out through thenozzle 21 of the-tube 20 holds the end of the tube above the moving webW so that only a flow of air engages the web. The tube and its nozzleprovide a first means for directing a stream of air against the surfaceof the moving web and the pivotal support for the tube and its switchprovide a second means for detecting the effect on the first means ofmovement of the web out of the running plane, and as the web dropsdownwardly, the tube will immediately pivot downwardly to actuate theswitch 22.

The tube 20 is shown in a running position in FIG- URE 2 and is movableto a threading position, as shown in FIGURE 4, for threading a fresh webW into the machine. A tube support is provided for simply raising thenozzle 21 and holding it in a raised position out of the way of the web.For this purpose, a threading air nozzle 29 is mounted on the bracket 23and supplied with air through a line 30 connected to the air supply S. Avalve 31 when opened permits air to flow through the nozzle 29 against areactance surface on a reactance plate 28 secured to the end of the tube20. The reactance plate 28 is positioned on the end of the tube oppositethe nozzle 21 so as to lift the nozzle.

As the valve 31 is opened the emerging air from the nozzle 29 forces thereactance plate 28 downwardly to pivot the tube against a stop 32 on thebracket 23 and the tube will be held in that position, as shown in FIG-URE 4, until the valve 31 is closed whereupon it will pivot back to therunning position of FIGURE 2.

In brief summary of operation, with reference to FIG- URE 1, the web Wmoves under tension in a machine in a reference plane as controlled byrollers or other support members and air escaping from a nozzle 11builds up a reactance air pressure in the conduit 10. When the webbreaks so that it loses tension and moves away from the nozzle 11 thenthe air pressure in the conduit 10 immediately drops to actuate apressure switch 15.

Thus it will be seen that I have provided improved mechanism meeting theobjectives and advantages above set forth for detecting the breakage ofa sheet. The mechanism is uncomplicated and reliable in construction andis capable of operating in adverse environments. The mechanism requiresonly a supply of air under pressure and it is well suited to operationover a range of pressures. It will be understood that the mechanism canbe placed in various positions relative to a moving web and is suited touse for detecting of breakage and lose tension of various movingelements.

In FIGURES and 6 a modification of the arrangement of FIGURES 2 through4 is illustrated. A movably supported conduit 20' has an open nozzle 21at its end with a flow of air emitting from the nozzle and the reactionof the air stream on the web W supports the nozzle in the position shownin FIGURE 5. With breakage of the web the nozzle and its supportingconduit 20 swing down tothe position of FIGURE 6.

Air flows into {the conduit 20' in somewhat the same manner as thearrangement of FIGURES 2 through 4 and a hollow tube 24 is pivotallysupported in a horizontal cylindrical opening in a bracket 23' in thesame manner as the arrangement illustrated in FIGURES 2 4 through 4.Instead of the air being supplied through the end of a tube however, airis supplied laterally through passages 36 in the bracket to flow intothe tube 24' through valve ports 37 and the passages 36 are suppliedfrom an air supply line 35 connected to a supply S. The tube 24 with itsports constitutes a valve and the position of the ports 337 permits airto flow into the conduit 20' in the first position of the conduit asshown in FIG- URE 5, and restricts or cuts off the flow of air in theposition of the conduit shown in FIG. 6. The result of the cutting offof the air flow creates an increase in pressure in the supply line 35actuating a pressure switch 38 to thereby manifest the break in the webW. It will be recognized that while the pressure switch 38 is thepreferred form of detecting the effect on the flow of air through theline 35 due to the shutting off of the valve provided by the tube 24,other means of detecting the effect on air flow may be used. Similarlywhile the pressure sensitive switch 15 of the arrangement of FIGURE 1 isthe preferred form of detecting the change in air flow due to breakageof the web, other means may be provided to detect the effect on airflow.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. A mechanism for detecting a break in a web comprising a flow conduithaving an orifice for directing a stream of air against the surface of aweb moving in a normal running plane with said stream forming an anglewith said running plane and directed toward the oncoming web with theweb surface providing a resistance to the escaping air, an air supplysource connected to said conduit, a pressure regulator in said conduitto maintain the air supply at a substantially uniform pressure, and apressure responsive device connected to the conduit downstream of thepressure regulator indicating change in pressure due to movement of theweb out of said running plane so that a break in the web will bedetected.

2. A mechanism for detecting a break in a web normally travelling in apredetermined running plane comprising a fluid flow conduit having anescape nozzle for directing a stream of fluid against the surface of aweb in a normal running plane, a pivotal mounting for said conduitsupporting the conduit for free pivotal movement about an axis generallyparallel to said plane of the web so that the reactive flow of the fluidemerging from the nozzle will support the nozzle at a position spacedfrom the surface of the web, and an electrical switch connected to theconduit and actuated by movement thereof for detecting movement of theweb out of said plane.

3. A mechanism for detecting a break in a web normally travelling in apredetermined running position comprising a flow nozzle having anorifice for directing a stream of fluid against the surface of the web,means movably supporting said nozzle so that the running position of thenozzle will be determined by the reactive force of fluid flowing againstthe web, means responsive to the running position of said nozzle so thatmovement of the web from said running plane is detected, said nozzlemovable between a running position adjacent the web and a threadingposition away from said running position so that a fresh web may beplaced in said running plane without interference with the nozzle, and areleasable support for holding said nozzle in said threading position.

4. A mechanism for detecting a break in a web normally travelling in apredetermined running position comprising an air flow conduit having anescape nozzle for directing a stream of air against the surface of theweb in a normal running plane, a pivotal mounting for said conduitsupporting the conduit for free pivotal movement about an axis parallelto said plane of the web so that the reactive force of the air emergingfrom the nozzle will support the nozzle at a position spaced from thesurface of the web, an air supply connected to said conduit, meansresponsive to the pivotal position of the conduit for detecting movementof the web out of the running plane, a reactance member having a surfaceconnected to said conduit positioned to pivot the conduit and nozzle toa threading position away from said plane, and a valve controlledthreading air nozzle connected to the air supply and positioned todirect the flow of air against said reactance surface for moving thenozzle to threading position.

5. A mechanism for detecting a break in a web comprising a flow conduithaving an orifice for directing a stream of air against the surface of aweb moving in a normal running plane with said stream forming an anglewith said running plane and directed toward the oncoming web at an anglebeing in the range of 60 'to 80 with the web surface providing aresistance to the escaping air, an air supply source connected to saidconduit, a pressure regulator in said conduit to maintain the air supplyat a substantially uniform pressure, and a pressure responsive deviceconnected to the conduit downstream of the pressure regulator indicatingchange in pressure due to movement of the web out of said running planeso that a break in the web will be detected.

6. A mechanism for detecting a break in a web normally travelling in apredetermined running position comprising, a fluid pressure devicehaving a pivotally supported member with an orifice thereon positionedadjacent said running position to direct the flow of fluid against thesurface of the web and support a pivotal running position of the memberdue to the-reaction of the air against the web, said orifice spaced fromthe pivotal support of the member in a direction of web travel away fromsaid pivotal support, fluid supply means connected to said device, anoperating circuit, an operating switch connected in said circuit, and aswitch actuator connected to said device and operated by changes in thedevice produced by movement of said web away from said running positionand affecting the flow of fluid from said orifice.

7. A mechanism for detecting a break in a web normally travelling in apredetermined running position comprising, a pivotally supportedelongate member extending in the direction of web travel having anorifice at its free end positioned adjacent said running position todirect a flow of fluid against the surface of the web and held in itspivotal position by the reactive force of the flowing fluid due to itsengagement with the surface of the web, means acting in response to achange in distance between the web and nozzle to manifest the change inposition of the web from the running position, and a control circuitoperated by said means when said web changes its position to affect theflow of fluid from the orifice.

8. A mechanism for detecting a break in a web normally travelling in apredetermined running plane comprising, a fluid flow nozzle tube havingan escape nozzle for directing a stream of fluid against the surface ofa web in a normal running plane, a pivotal mounting for said tubesupporting the tube for free pivotal movement so that the reactive flowof the fluid emerging from the nozzle will support the nozzle at apivotal position spaced from the surface of the web, and an electricalmercury switch mounted on the nozzle tube and actuated by movementthereof for detecting movement of the tube due to movement of the webout of said plane.

References Cited in the file of this patent UNITED STATES PATENTS1,604,138 Vidaver Oct. 26, 1926 2,077,525 Mennesson Apr. 20, 19372,244,864 Witham June 10, 1941 2,438,696 Fox et al Mar. 30, 19482,728,223 Herrman Dec. 27, 1955 2,891,686 Roberson et a1. June 23, 19593,115,037 Forrester Dec. 24, 1963 FOREIGN PATENTS 750,341 Great BritainJune 13, 1956

1. A MECHANISM FOR DETECTING A BREAK IN A WEB COMPRISING A FLOW CONDUITHAVING AN ORIFICE FOR DIRECTING A STREAM OF AIR AGAINST THE SURFACE OF AWEB MOVING IN A NORMAL RUNNING PLANE WITH SAID STREAM FORMING AN ANGLEWITH SAID RUNNING PLANE AND DIRECTED TOWARD THE ONCOMING WEB WITH THEWEB SURFACE PROVIDING A RESISTANCE TO THE ESCAPING AIR, AN AIR SUPPLYSOURCE CONNECTED TO SAID CONDUIT, A PRESSURE REGULATOR IN SAID CONDUITTO MAINTAIN THE AIR SUPPLY AT A SUBSTANTIALLY UNIFORM PRESSURE, AND APRESSURE RESPONSIVE DEVICE CONNECTED TO THE CONDUIT DOWNSTREAM OF THEPRESSURE REGULATOR INDICATING CHANGE